The present invention relates to plant genetic engineering and more particularly to selective gene expression in plants. The cauliflower mosaic virus (CaMV) 35S promoter has been shown to be highly active in most plant organs and during most stages of development when integrated into the genome of transgenic plants (Odell et al., 1985; Nagy et al., 1985; Jensen et al., 1986; Kay et al., 1987; Jefferson et al., 1987; Sanders et al., 1987). The CaMV 35S promoter can also confer expression in protoplasts of both dicots and monocots (On-Lee et al., 1985; Fromm et al., 1985; Ow et al., 1987; Nagata et al., 1987; Odell et al., 1988). However, it is not strictly an unbiased constitutive promoter. When expression was analyzed in floral tissue by histochemical localization, differences in expression levels between adjacent cells were observed. Differences have also been observed in the expression pattern of the same CaMV 35S promoter construct in independent transgenic plants and in different plant species. These observations suggest that the 35S promoter may contain several cis-elements which differentially interact with trans factors responsible for expression in different cell types.
It is therefore an object of the present invention to provide modified plant promoters which are useful to cause selective expression of chimeric plant genes in plant tissues.
It is therefore another object of the present invention to provide modified CaMV 35S promoters which are useful to cause selective expression of chimeric plant genes in plant tissues.
These and other objects and advantages of the present invention will become apparent from the following description and exemplary embodiments.